The Khao Khiao Massif (Thai: เขาเขียว, pronounced [kʰǎw kʰǐa̯w]) is a moderately high mountain range near Chonburi, eastern Thailand.

[1] This massif has the last substantial forested zone in Chonburi Province, a region that is much affected by urbanization and other forms of human intervention and land degradation.

Khao Khiao is the mountain area closest to Bangkok, rising about 70 km to the southeast of the capital.

Founded in 1974, it is an IUCN Category IV wildlife sanctuary, measuring 145 square kilometres (56 sq mi) in area.

[2] The Khao Kheow Open Zoo is at the foot of the mountain massif on its southern side.